The present invention relates to a method and apparatus which is used to retain spinal and/or pelvic elements, such as vertebrae for example, in a desired spatial relationship.
A known apparatus for retaining vertebrae in a desired spatial relationship is disclosed in U.S. Pat. No. 4,648,388. The apparatus includes a plurality of threaded fasteners which are connected with vertebrae of a human spinal column. Retaining rods are bent to a configuration which is a function of the desired spatial relationship between vertebrae of the spinal column. After a rod has been bent to the desired configuration, it is inserted into clamps connected with the fasteners. The clamps are then engaged to hold the vertebrae against movement relative to the rod. Other known apparatus for retaining vertebrae in a desired spatial relationship are disclosed in U.S. Pat. Nos. 4,611,581; 4,655,199; and 4,887,595.
With this known apparatus, once the threaded fasteners or bone screws have been connected with the vertebrae, it is difficult to adjust the position of a retaining rod relative to the fasteners. This is because once the fasteners or bone screws have been connected with the vertebrae, each of the fasteners remains stationary relative to the vertebra with which it is connected. The clamps which interconnect the retainer rod and the fasteners cannot be adjusted to change the spatial relationship between the fasteners and the retainer rod.